CaptionStack
Private by design

TTML TO JSON

TTML to JSON.

Convert TTML (.ttml) subtitles to JSON (.json) in seconds. No upload, no sign-up, nothing leaves your browser.

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1

Choose your caption file

We’ll detect the format automatically. Drop several files to convert them all at once.

Don’t have a file handy?
2

Choose an output format

Select what you need on the other side.

100% privateYour files never leave this device.
8 formatsBuilt for the caption formats you use.
No limitsConvert as often as you need.

How to convert TTML to JSON

  1. Drop your .ttml file into the converter above, or click to browse. Several files at once become a ZIP.
  2. Check the quality report and fix timing or text in the editor if you need to.
  3. JSON is already selected as the output format. Click Download converted file.

Conversion happens entirely in your browser. Nothing is uploaded, no account is needed, and there is no file count limit.

About TTML (.ttml)

Timed Text Markup Language is a W3C XML format for captions and subtitles. It underpins broadcast standards such as EBU-TT and IMSC and is required by many streaming platforms and accessibility regulations. Each <p> element carries begin and end (or dur) attributes and the caption text.

About JSON (.json)

JSON is the easiest format to consume from code. CaptionStack reads an array of cue objects or an object with a cues array, accepts timestamps as milliseconds or time strings, and writes a versioned document with millisecond start and end values so you can load captions straight into a web app, database, or analytics pipeline.

What changes when converting TTML to JSON

Lossless for timing, text, and identifiers. Timestamps are exported as integer milliseconds.

Frequently asked questions

Is this TTML to JSON converter free?
Yes. CaptionStack is free and open source, with no limits on file count or conversions.
Are my caption files uploaded anywhere?
No. Parsing and conversion run in your browser using a local Web Worker. Your files never leave your device.
Can I edit the captions before exporting to JSON?
Yes. After import, open the editor to adjust start and end times, fix text, split, merge, or reorder cues. The quality report flags overlaps, short cues, and fast reading speeds with one-click fixes.
Can I convert many .ttml files to .json at once?
Yes. Drop multiple files and download all of the results as a single ZIP archive.

Other TTML conversions

Other ways to get JSON

All caption formats